Heat dissipator



Mardl 1958 D. B. KAISER ETAL HEAT DISSIPATOR Filed April 29, 1966 1NTORS United States Patent Ofiice 3,372,741 Patented Mar. 12, 19683,372,741 HEAT DISSIPATOR Donald B. Kaiser and Robert Roth, Lancaster,Pa., as-

signors to Radio Corporation of America, a corporation of Delaware FiledApr. 29, 1966, Ser. No. 546,254 Claims. (Cl. 16580) ABSTRACT OF THEDISCLOSURE Heat dissipator comprising helices of wire formed intostacked closed loops and confined in an annular space defined by outerand inner concentric metal sleeves. The turns of each helix adjacent tothe inner sleeve are in substantially mutual contact relation.

on the object to be cooled.

For achieving this object, a heat dissipator is provided comprising aclosed loop formed from an elongated helix of wire. For directing theflow of a cooling medium through the dissipator, as well as forimparting greater strength thereto, impervious stiffening means joiningvarious turns of the helix to one another is provided. In a preferredembodiment, the dissipator comprises a plurality of loops rigidly joinedtogether in stacked, coaxial relation.

In the drawings:

FIG. 1 is a view in perspective, and partly schematic, of the heatdissipator;

FIG. 2 is a side elevation, partly broken away, of an electron tubehaving the heat dissipator shown in FIG. 1 and a further heat dissipatorshown in FIG. 6 mounted thereon;

FIG. 3 is a fragmentary view of a different embodiment of a dissipatormounted on an electron tube;

FIG. 4 is a sectional view of an assembly jig containing the variousparts of the heat dissipator shown in FIG. 1 mounted therein;

FIG. 5 is a sectional view along line 55 of FIG. 4;

FIG. 6 is a sectional view of a further embodiment of a heat dissipator;and

FIG. 7 is a sectional view of a still further embodiment of a heatdissipator.

With reference to FIGS. 1, 4 and 5, a heat dissipator 10 comprises aplurality of wire helices 12 each formed into a closed, circular loop.14. The loops 14 are in stacked, coaxial relation. The turns of thehelices are in the shape of elongated rectangles having long sides 18and short sides 19, with the long sides 18 extending substantiallyperpendicular to the axis of the loops. The loops 14 are maintained inspaced apart relation by means of spacer rings 20 and 22 disposedbetween and bonded to adjacent pairs of loops. Bonded to the inner andouter portions of the loops are inner and outer stiffening cylindricalsleeves 24 and 26, respectively. One purpose of the sleeves 24 and 26 isto provide a rigid assembly which may be readily and rigidly mounted onan object to be cooled, as described hereinafter.

The helices 12 and the sleeves 24 and 26 are made from good thermalconductivity materials such as copper. and copper clad steel,respectively.

In the use of the heat dissipator 10, the dissipator may be mounted on,for example, the cylindrical anode 30 of a commercial electron tube 32,shown in FIG. 2, such as an RCA 7213 or RCA 8437. Preferably, for goodheat transfer between the tube anode 30 and the dissipator 10, the innersleeve 24 of the dissipator is soldered to the anode. Although notshown, the tube 32 can be mounted in apparatus providing a forced flowof air, as by a blower, in the direction of the arrows 34. The sleeves24 and 26 direct the air longitudinally through the dissipator 10. Theelongated rectangular shape of the helix turns provides a high ratio ofcooling area (the surface area of the long sides 18 and the outer shortsides 19 of the helix turns) to heated area (the surface area of theshort sides 19 bonded to the inner cylinder 24 engaged, in turn, withthe object being cooled). Preferably, the loop helices have a smallturns pitch so that the inner short sides 19 of the helix turnspractically touch one another and provide a substantially continuoussurface contact of the loops 14 with the inner sleeve 24. The dissipator10 structure possesses great strength, whereby exceptionally largecooling to heated area ratios may be provided for large capacity heatdissipation.

In another embodiment, shown in FIG. 3, a heat dissipator 36 comprisesloops 38 formed from wire helices having triangular-shaped turns. Theloops 38 are bonded between inner and outer sleeves 40 and 42,respectively. Preferably, the loop helices are wound with such a smallturns pitch that the helix turns touch one another and form asubstantially continuous surface in contact with the inner sleeve 40.The close turns winding prevents penetration or entanglement of the baseportions; of the helix turns of adjacent loops with one another duringmanufacture of the dissipator. Spacer rings are thus not requiredbetween adjacent loops adjacent to the inner sleeve 40. Spacer rings 44are used between adjacent loops 38 adjacent to the outer sleeve 42 tomaintain the apex portions of the helix turns in proper spaced relationduring fabrication of the dissipator 36, and to provide a more rigiddissipator assembly.

For manufacturing the heat dissipator 10, a wire of a good heatconductive material, such as copper, is wound in an elongated helix 12around and along an elongated rectangular mandrel, not shown. Tomanufacture the heat dissipator 36, a triangular mandrel is used.Preferably, the mandrel is built-up of three dovetailing tapered memberswhich are slidable relative to one another. Thus, upon completion of thewinding, the mandrel may be collapsed to facilitate removal of the helixtherefrom. Mandrels of the type described and means for winding a helixtherearound are known in the art.

After the wire is wound into a helix 12 on the mandrel, the woundmandrel may then be pressed into a forming die, not shown, to closelyconform the helix turns to the shape of the mandrel. An advantage of theuse of copper wire is that it is quite ductile. After the pressingoperation, the wire helix 12, while still on the mandrel, may then bemachined, as by grinding, to provide the helix with accurate externaldimensions. These pressing and machining steps provide an accurate fitof the helix loops v14 within the sleeves 24 and 26 in the completeddissipator assembly, with the short sides 19 of the helix turns in fullsurface contact (through an intermediate layer of solder) with thesleeves 24 and 26.

The winding mandrel is then collapsed and the helix 12 removedtherefrom. The helix 12 is then formed into a closed loop 14 by fixingthe end turns of the helix to one another. A simple means to accomplishthis, as shown in FIG. 5, is to insert the two ends 50 and 52 of thehelix wire into the opposite ends of a metal tubing 54, and then pinchthe tubing onto the wire ends.

For assembling a number of helix loops 14 into a dissipat-or 10, anassembling jig 56, as shown in FIG. 4, can be used. The jig 56 comprisesa base member 58, an outer wall 60, a central platform 62, and aremovable annular top plate 66.

In the assembly of the dissipator .10, the two sleeves 24 and 26 arefirst inserted into the jig 56 into engagement with the outer wall 60and the platform 62 of the jig, respectively. Two thin walled cylinders70 and 72 of a solder material are then placed in the jig in engagementwith the inner and outer sleeves 24 and 26, respectively. A helix loop14 is then placed in the bottom of the jig 56 between the cylinders 70and 72. Preferably, the helix loop 14 fits snugly therebetween. Twospacer rings 29 and 22 are then dropped into the jig into engagementwith the helix loop 14 adjacent to the inner and outer portions thereof.Further helix loops 14 and spacer rings 20 and 22 are then alternatelyloaded into the jig to build up the dissipator to the desired size, asshown. The top plate 66 is then loaded into the jig into engagement withthe top loop 14 to press the various members in the jig into firmengagement with one another. The loaded jig is then passed through afurnace to melt the solder cylinders 70 and 72 to solder the loops 14,the spacer rings 20 and 22, and the sleeves 24 and 26 to one another attheir contacting points.

Using a copper wire and copper clad steel sleeves 24 and 26, a solderknown as BT solder and comprising a copper-silver eutectic can be used.The jig 56 is made of a material non-wettable by the solder, such as achromeiron alloy which has been surface oxidized.

With reference to FIG. 6, a heat dissipator 80 is shown comprising ahelix of wire formed into a circular closed loop 82. For strengtheningand stiffening the dissipator 80 and for directing the flow of a coolingmedium therethrough, annular plates or washers 84 and 86 lying in planessubstantially perpendicular to the axis of the loop 82 are bonded toopposite sides of the loop.

In use, the dissipator 80 can be mounted, for example, on one end of thetube 32 shown in FIG. 2 by soldering the washer 86 to the tube envelope.Cooling air passes into the dissipator 80 through the central opening ofthe end washer 84 and then radially outwardly through the dissipator.

In the manufacture of the dissipator 80, an elongated helix 82 may bewound in the same manner as described in connection with the winding ofthe helices 12 for the dissipator 10. A jig of the type shown in FIG. 4may be used. A first washer 84 is first dropped into the bottom of thejig, a closed helix loop 82 then placed in the jig on top of the washer84, and the second washer 86 then placed on top of the helixloop 82.Solder is provided, for example, by means of a solder cladding on thewashers 84 and 86. A jig cover plate is used to maintain the parts "inengagement, and the jig is heated to melt the solder to solder the partstogether.

With reference to FIG. 7, a heat dissipator 90 comprises two concentricloops 92 and 94 spaced apart by a spacer assembly 96. The spacerassembly comprises two rings 98 and maintained in coaxial, spaced apartrelation by spaced apart brace members 102. The loops 92 and 94- aremounted between stiffening annular plates or Washers 106 and 108.

The manufacture of the dissipator 98 is similar to the manufacture ofthe dissipator 80 except that the two loops 92 and 94, and the spacerassembly 96 are loaded into the jig between the two washers 106 and 108.

What is claimed is:

1. A heat dissipator comprising:

(a) inner and outer concentric metal sleeves defining an annular spacetherebetween, and

(b) a plurality of helices of wire formed into closed loops stackedconcentrically with said sleeves in said annular space and lying inplanes normal to the axis of said sleeves, each turn of said helicesbeing bond ed t said inner and outer metal sleeves.

2. A heat dissipator as in claim 1 and wherein adjacent turns of saidhelices are substantially in mutual contact adjacent to said innersleeve for forming a substantially continuous contact of said heliceswith said inner sleeve.

3. A heat dissipator as in claim 1 including:

two closed wire helix loops, and

spacer means bonded to each and between adjacent ones of said loops formaintaining said loops in spaced apart relation.

4. A heat dissipator as in claim 3 wherein said loops are circular andare in coaxial side-by-side relation, and said stiflening meanscomprises a tubular sleeve bonded to the radially inner portions of saidloops and a tubular sleeve bonded to the radially outer portions of saidloops.

5. A heat dissipator as in claim 1 wherein the turns of said helices aretriangular in shape with the base portions of said turns engaged withthe inner one of said sleeves.

References Cited UNITED STATES PATENTS 3,217,392 11/1965 Roffelsen -4843,327,779 6/1967 Jacoby 165'80 FOREIGN PATENTS 479,887 2/1938 GreatBritain.

ROBERT A. OLEARY, Primary Examiner.

C. SUKALO, Assistant Examiner,

